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P. Manoj Kumar ¹, A. C. Narayana ¹, R. Tatavarti ²

Affiliations
1 Department of Marine Geology & Geophysics, Cochin University of Science & Technology, Fine Arts Avenue, Cochin - 682 016, IN
2 Naval, Physical & Oceanographic Laboratory, Thrikkakara, Cochin - 682 021, IN

Abstract

Surface sediment particle sizes, their spatial distribution and their geotechnical characteristics in the Ambalapuzha-Purakkad Mudbank were studied, based on field observations during pre-monsoon and monsoon seasons. The study revealed that sediments in the mudbank are clayey silts in both the seasons. The magnitude of the fine silt and clay contents blanketing the ocean bed were however, observed to be more in the pre-monsoon season indicating the possibility of fine silt and clay going into suspension during the monsoon season. Geotechnical properties of surface sediments revealed that they are highly plastic, with high liquid limits. Organic carbon, fine silt and clay minerals play an important role in the behaviour of mudbank sediments.

Keywords

Sedimentology, Mudbank Dynamics, Southwest Coast of India.

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A. C. Narayana ¹, K. Pandarinath ¹, A. R. Karbasi ¹, B. R. Raghavan ¹

Affiliations
1 Department of Marine Geology, Manga]ore University, Mangalagangotri, Karnataka 574 199, IN

Abstract

Moderately well-sorted silica sands of aeolian origin occur at various locations along the South Kanara coast. They contain a very low percentage of heavy minerals. The silica content is comparatively more in the medium-size fraction than in the finer fraction. Higher concentrations of AI, Fe, and Ti are associated with finer fractions. The average silica content (96.6%) shows that these white sands are of high grade quality. The very low magnetic susceptibility values are indicative of low Fe content.

Keywords

Silica Sand, South Kanara, Karnataka, Sedimentology.

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A. C. Narayana ¹, K. Pandarinath ¹

Affiliations
1 Department of Marine Geology, Mangalore University, Mangalagangotri 574 199, Karnataka, IN

Abstract

Grain-size statistics are employed in sediment transport studies. The alongshore transport of sediment in shallow regions (30-50m depth) and deeper regions (>l50m depth) is in north and south directions, whereas in the depth range of 50-75m, the sediment transport direction is towards the south. The onshore-offshore sediment transport study reveals that the sediment transport direction is towards onshore where fluvial influence is absent and the direction is towards both onshore and offshore where the fluvial influence is prevalent. The studies further reveal the different energy regimes of transportation.

Keywords

Sedimentology, Grain-Size Statistics, West Coast, Mangalore, Continental Shelf, Karnataka.

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A. C. Narayana ¹, K. N. Suresh Kumar ¹

Affiliations
1 Marine Geology Division, Cochin University of Science & Technology, Cochin-682016, IN

Abstract

Four sediment facies viz., sand, clayey sand, sandy clay and silty clay occur in Kumbla-Shiriya (K-S) estuary. Sediments have formed from bottom suspension and graded and uniform suspension as a result of variable hydraulic conditions in different parts of the estuary. Kaolinite+chlorite is the dominant clay mineral followed by montmorillonite and illite. Gibbsite, goethite and quartz also occur in minor quantities. It appears that the abundance and distribution of clay minerals in the estuary are controlled by the geology of the source area and the water circulation pattern within the estuary.

Keywords

Clay Mineralogy, Sedimentology, Kumbla-Shiriya Estuary, Southwest Coast of India.

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A. C. Narayana ¹, Venkatesh Prabhu ²

Affiliations
1 School of Marine Sciences, Cochin University of Science & Technology Cochin - 682 016, IN
2 Department of Marine Geology, Mangalore University, Mangalagangotri - 574 199, IN

Abstract

The textural and geochemical studies of shelf sediments off Honavar reveal three types of sedimenents - modern, relict and mixture. Modern sediments are present in the inner as well as outer shelf regions. The midshelf region mostly consists of relict sands. In general, the distribution pattern of Cu and Ni shows the zonal pattern as that of three types of sediments i.e., modern, relict and mixture. Cu, Ni, and Zn show high positive correlation with organic matter. Factor analysis reveals that the sedinients were derived from a terrigenous source and deposited in an oxidizing environment.

Keywords

Honavar, Geochemical Studies, Relict Sediments, West Coast.

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C. P. Priju ¹, A. C. Narayana ¹

Affiliations
1 Department of Marine Geology & Geophysics, Cochin University of Science & Technology, Cochin -682 016, IN

Abstract

In this paper, we present the textural characteristics, and Tanner's bivariate plots of grain size parameters to understand the depositional processes in a lagoonal system during the Late Holocene. For this purpose, 16 core samples recovered from the Vembanad lagoon, the largest backwater system on the west coast of India, were investigated. In northern and southern sectors of the lagoon, sand is the dominant textural facies, while in the central sector mixed textural facies - muddy sand and sandy mud - are prevalent. Suite statistics suggest that open- and closed-basin conditions prevailed, which punctuated the high and low energy conditions. High-energy conditions prevailed in northern and southern parts of the lagoon, particularly in areas close to the river mouths. Other parts of the lagoon exhibit low to moderate energy regime and open-to-restricted estuarine conditions. The study emphasizes that the bivariate plot is an extremely useful tool in distinguishing between open- and closed basin conditions in coastal environments.

Keywords

Sedimentological studies, Depositional environments, Vembanad Lagoon, Kerala, Southwest coast of India.

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A. C. Narayana ¹

Affiliations
1 Department of Marine Geology and Geophysics, Cochin University of Science and Technology, Cochin- 682016, IN

Abstract

No Abstract.

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A. C. Narayana

Abstract

No Abstract.

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K. S. Valdiya ¹, A. C. Narayana ²

Affiliations
1 Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore - 560 064, IN
2 Department of Marine Geology and Geophysics, Cochin University of Science and Technology, Cochin - 682 016, IN

Abstract

The drainage pattern in the Proterozolic terrane of central Kerala in southwestern Peninsular India reflects control of WNW-ESE, N-S and NNW-SSE oriented lineaments, many of which are recognized as faults. Reactivation of these faults of Precambrian antiquity manifested itself in strike-slip and oblique-slip movements as evident from (1) their demarcating straight linear hills and ridges having steep slopes or escarpments that are characterized by exposure of remarkably fresh Proterozoic rocks on rectangular planar slopes and triangular facets cut by sparse gullies or straight furrows of recent origin, (11) swerving of rivers and streams and change of their original meandering system to the one characterized by peculiar loops, and (111) occurrence of epicentres of historical earthquakes (numbering 60) on or close to the faults. The Quaternary sediments in the 83 km long Vembanad Lagoon, roughly paralleling a NNW-SSE trending lineament-demarcated ridge, bear testimony to intermittent subsidence and attendant drowning of the land, attracting six rivers to discharge their waters and sediments in the resulting depression, without forming deltas at their mouths.

Neotectonic activity along the NNW-SSE, N-S and WNW-ESE oriented active faults is manifest in abrupt bending of a11 the six rivers along them, forming loops of a variety of shape, their intimate association with lacustrine clays and muds deposited in the past, and the present-day ponding of rivers and their tributaries upstream of the crossing of the active faults. Extending upstream for hundreds to thousands of metres-as much as 4 to 7 km in a few cases-the stagnant bodies of water in the river and stream channels imply continuing movement along faults of the Proterozoic terrane.

Keywords

Seismicity, Stream ponding, Fault reactivation, Oblique-Slip movement, Palaeolake, Kerala.

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A. C. Narayana ¹, C. P. Priju ¹

Affiliations
1 Department of Marine Geology and Geophysics, Cochin University of Science & Technology, Lakeside Campus, Cochin - 682 0 1 6, IN

Abstract

The coastal landforms and land use/Land cover changes of central Kerala have been studied with the aid of topographic maps, satellite images and extensive field checks. The landforms identified are barrier islands, beach ridges and swales, strandlines, flood plains and marshy swamps. Several parallely positioned barrier islands and paleo-Beach ridges reveal that the central Kerala coast has been prograding. It is observed that the evolution of coastal landforms is influenced by the fall in sea level and/or uplift of the coast. Extensive occurrence of strandline/Chenier deposits supports the view that the rivers of central Kerala once have supplied enormous amount of sediments.

Land use/Land cover changes, which have occurred during 1966-1995 are quite alarming. The reduction of about 50% in both flood plain and river channel area is due to changes in the land use pattern. Significant changes in the shoreline and morphology of river mouths are recorded. Area of accretional shoreline is more than that of erosion-Prone shoreline. Major morphological changes are observed near the Cochin inlet. The factors affecting the shoreline and landform changes are natural as well as anthropogenic. The natural processes affecting the shoreline changes are sediment supply, coastal processes, and anthropogenic activities such as dredging. Important factors affecting the land use/Land cover changes are reclamation of land for agricultural and industrial purposes, and sand mining in riverbeds and paleostrandline areas.

Keywords

Coastal Landforms, Shoreline Changes, Paleostrandlines, Remote Sensing, Kerala Coast.

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A. C. Narayana ¹, R. Tatavarti ², Mudrika Shakdwipe ¹

Affiliations
1 Department of Marine Geology and Geophysics, School of Marine Sciences, Cochin University of Science and Technology, Lakeside Campus, Fine Arts Avenue, Cochin - 682 086, IN
2 Naval Physical and Oceanographic Laboratory, Defence Research and Development Organisation, Cochin - 682 921, IN

Abstract

No Abstract.

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A. C. Narayana ¹

Affiliations
1 Dept of Marine Geology and Geophysics, Cochin University of Science and Technology, Fine Arts Avenue, Cochin - 682 016, IN

Abstract

No Abstract.

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A. C. Narayana ¹, R. Tatavarti ²

Affiliations
1 Cochin University of Science and Technology, Cochin - 682 016, IN
2 Naval Physical and Oceanography Lab., Cochin - 682 022, IN

Abstract

No Abstract.

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A. C. Narayana ¹, C. P. Priju ¹, A. Chakrabarti ²

Affiliations
1 Department of Marine Geology and Geophysics, Cochin University of Science and Technology, Lakeside Campus, Kochi - 682 016, IN
2 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur - 721 302, IN

Abstract

No Abstract.

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A. C. Narayana ¹

Affiliations
1 Department of Marine Geology & Geophysics, School of Marine Sciences, Cochin University of Science& Technology, Lakeside Campus, Cochin 682 016,, IN

Abstract

Because of the direct connection between rainfall and both erosion and transport of sediments, variations in rainfall are likely to affect both processes Factors governing rainfall variation during the last 100 years, and the role played by rainfall in erosion and fluvial sediment discharge of Kerala fivers during the last 20 years have been investigated Rainfall variation during the last 100 years over Kerala suggests that the annual rainfall has decreased in the last five decades Geographical variation is also documented with a higher rainfall in northern Kerala Further, physiography, particularly the Sahyadri (Western Ghats) mountain range, plays an important role in the spatial distribution of rainfall There is a positive relation between rainfall variability run-off and sediment discharge of the rivers of Kerala It can be suggested that the geomorphic features of the landscape play an important role in the supply, transport and deposition of sediments in coastal areas, including continental shelf.

Keywords

Sediment Discharge, Rainfall Variability, Monsoon, Kerala.

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V. Kameshwara Rao ¹, A. C. Narayana ¹

Affiliations
1 Centre for Earth and Space Sciences, University of Hyderabad, Hyderabad 500 046, IN

Abstract

Nonlinear geostatistics is commonly used in ore grade estimation and seldom used in lithological characterization. Categorization of lithological units is essential in ore grade estimation, and this can be done based on the lithological information obtained from drill-hole data. In general, a conventional classification method was used to delineate different lithological units using geological cross-sections derived from borehole logs. In this study, we suggest an approach based on geostatistical nonlinear indicator kriging (IK) to delineate different lithological units of an iron ore deposit. Iron ore has been broadly grouped into eight litho units based on physical and chemical characteristics of the core samples recovered from drill holes during exploration stage. IK helps in the construction of litho maps for different benches of the mining deposit. Fe grades were estimated using ordinary kriging model and grade maps were prepared for all the benches of the deposit. A comparison was done between the grades of each litho type resulting from the two methods, i.e. IK model and geological cross-sectional model and the relative merits of the IK approach have also briefly discussed.

Keywords

Grade Estimation, Indicator Semi-Variograms, Indicator Kriging, Lithological Maps, Nonlinear Geostatistics.

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K. Pandarinath ¹, A. C. Narayana ²

Affiliations
1 Oceanography & Climate Studies Group, Physical Research Laboratory, Navrangpura, Ahmedabad- 380009, IN
2 Department of Marine Geology and Geophysics, Cochin University of Science & Technology, Fine Arts Avenue, Cochin - 682016

Abstract

The innershelf sediments of Coondapur were studied for Cu, Pb, Zn, Ni, Co, V, Mn, Cr, Fe, Ti, Al, Ca, organic matter composition and magnetic susceptibility to understand their distribution, enrichment and element burial phases in the sediments. Along most of the transects, the sediments of 30m depth have shown more concentrations of Cu, Zn, Ni, Co, Mn, Fe, Ca and organic matter than those of 20 and 10m depth. The comparisons with sediments of uncontaminated natural formations, innershelf sediments of other unpolluted regions and world averages in different geological formations shows that the study area is unpolluted and the data can be used as a base line for future pollution studies. The sequential leaching of elements shows that they are mainly (∼60-80% of the total content) associated in detrital clay and heavy minerals followed by (∼20-30% of the total) in sulphide phase. The concentrations of all the element (except Mn) in other phases (exchangeable ions, loosely sorbed ions, carbonate constituents and interstitial water) were negligible. Nearly 40% of the total Mn is present in the leachates of EDT A and acetic acid soluble fractions. Mn concentration is almost negligible (6-11 % of the total) in acetic acid-hydroxylamine hydrochloride leachate (oxide phase) and its concentration is considerable (10-30% of the total) in H₂O₂-ammonium acetate leachate (sulphide phase). These observations suggest that reducing conditions may be prevailing in the innershelf off Coondapur.

Keywords

Geochemistry, Pollution, Environment, West Coast of India, Karnataka.

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Vishwas S. Kale ¹, A. C. Narayana ², Manoj K. Jaiswal ³

Affiliations
1 Formerly at the Department of Geography, SP Pune University, Pune 411 007, IN
2 Centre for Earth, Ocean and Atmospheric Sciences, University of Hyderabad, Hyderabad 500 046, IN
3 Department of Earth Sciences, Indian Institute of Science Education and Research, Kolkata 741 246, IN

Abstract

Sand sheets and mounds occur along the eastern bank of Hagari River in Anantapur district, Andhra Pradesh, India. These wind-blown sands are considered to be deposited by a flood about 1–2 centuries ago. Based on the description in the British era District Gazetteer, we infer that the sands were most likely deposited by a flash flood in May 1851.

Keywords

Aeolian Sands, Buried Temples, Desertification, Flash Floods, Flood Deposits.

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